Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque

h, w = map(int, input().split())
maze = {(i,j):c for i in range(h) for j, c in enumerate(input())}

blacks = sum(c == '#' for c in maze.values())

def bfs(i, j):
    dq = deque()
    dq.appendleft((1, (i, j)))
    while dq:
        steps, (i, j) = dq.pop()
        if (i, j) == (h-1, w-1):
            return steps
        if maze.get((i, j), '#') == '#':
            continue
        maze[(i, j)] = '#'
        dirs = ((-1, 0), (1, 0), (0, 1), (0, -1))
        dq.extendleft((steps+1, (i+di, j+dj)) for di, dj in dirs)

res = bfs(0, 0)
print(-1 if res is None else h*w - res - blacks)